Trialkoxysilanes are used in the production of silane coupling agents. U.S. Pat. No. 3,641,077 teaches the preparation of trialkoxysilanes by directly reacting silicon metal with alcohol in the presence of a catalyst produced by sintering copper and silicon. However, this method results in low yields of trialkoxysilanes.
U.S. Pat. No. 3,775,457 teaches the production of alkoxysilanes from the reaction of an alcohol and finely divided silicon metal in the presence of a cuprous chloride catalyst. Although the use of cuprous chloride results in increased yield over that obtained using the sintered copper-silicon catalyst, the use of cuprous chloride catalyst also results in the formation of HCl which in turn necessitates the use of costly corosion resistant materials of construction for the reactor. Further, the presence of chloride in the reactor and in the product stream reduces the yield of trialkoxysilane by catalyzing the further reaction of trialkoxysilane with the alcohol to yield tetra-alkoxysilane. Also, when methanol is a reactant, the HCl resulting from the use of the cuprous chloride catalyst will react with some of the methanol to produce methyl chloride and water. This makes the cuprous chloride catalyzed reaction inefficient through the loss of methanol and the water can react with trialkoxysilanes to produce siloxanes. The presence of water in the reaction mixture can also inhibit the conversion of silicon metal.
Thus, there continues to exist the need for a process of directly reacting silicon metal and an alcohol to obtain trialkoxysilanes which process has increased yields of triakloxysilanes and yet avoids the above-mentioned deficiencies of the cuprous chloride process.